1. Field of the Invention
This invention relates to a method and apparatus for the remote measurement of the height distribution of wind direction and speed in the atmosphere by hybrid use of radio and acoustic waves.
2. Description of Prior Art
As method for the remote measurement of wind profiles up to the height of some hundred meters, say 200 m or so above the ground, a combined system of bistatic Doppler acoustic radars and a combined system of three radio acoustic sounding systems have been known in the art.
The former system, based on the principle that the atmospheric turbulent regions play a role as scatterers for incident acoustic waves, and that a Doppler acoustic radar has the capability of detecting the radial component of wind velocity as a function of distance from its receiver, accomplishes the measurement of wind profiles up to the height of several hundred meters. (Robert L. Peace, Jr. "The XONDAR", The Boulder Inter-Comparison Experiment, pages 87-97, June 1980). This system, however, requires a considerably large place, at least an area enclosed by an equilateral triangle with sides 200 m long, for the installation of the whole system on the ground. Moreover, ground clutter due to side lobes of the acoustic antenna causes interference for the operation of this system.
The latter system proposed by the present inventors consists of three radio acoustic sounding systems (RASSs "A", "B", and "C"); one of them (e.g. RASS "B") is directed for the vertical and the other two (RASSs "A" and "C") for high elevation angles of two orthogonal directions. In this arrangement, RASS "B" measures the Doppler shift frequencies corresponding to the height distribution of the atmospheric temperature and RASSs "A" and "C" measure the Doppler shift frequencies corresponding to that of the atmospheric temperature and each radial component of the wind velocity. Such a set of measurements of Doppler shift frequencies by RASSs "A", "B" and "C" provides the height distribution of wind direction and speed, and that of atmospheric temperature. (Japanese Patent Application Disclosure No. 140181/1980). This system, however, suffers from the limitation of the range of measurable wind speed and inevitably necessitates use of special devices for the detection of Doppler shift frequencies.